Green: Look, Time Impact, SPD-SL, Speedplay, Look Keo and Delta

Red: SPD, Time Atac, Speedplay Frog and Crank Brothers Egg Beater systems

Blue: SPD-R only
The above diagram shows the 3 most common cleat patterns, the highlighted dots in Green are referred to as 3 bolts Look fitment, the Red are known as 2 bolt SPD fitment and Blue dots are SPD-R fitment only.

These are the 3 most used terms but they will fit other pedal types.  Green will fit Time Impact, SPD-SL, Speedplay, Look Keo and Delta.  Red will fit SPD, Time Atac, Speedplay Frog and Crank Brothers Egg Beater systems.  The Blue will only accept SPD-R pedal types.